Turbocompressors are primary energy consumers in aeration processes. For example, fifty to seventy percent of the electric power consumed in a waste water treatment plant is attributable to the energy required for aeration. To place this in perspective, it is not uncommon for the treatment of waste water to be thirty five percent of the total energy consumed by a municipality, including street lighting, heating and cooling. It is therefore desirable to find means to improve the energy efficiency and capital costs of treatment processes in general. In the past, the focus of process optimization has been finding ways to improve diffuser technology, blower efficiency and air control.
Optimal processes commonly incorporate fine bubble diffusers, automated control of key parameters and blower designs which incorporate dual inlet and discharge vane control. Energy costs can be reduced by as much as fifty percent with fine bubble diffusers when compared to mechanical or coarse bubble diffusion. This is, in part, due to the fact that finer bubbles provide relatively high surface area which, in turn, results in greater friction with water. In turn, the bubbles rise more slowly, providing greater contact time with the water. Transfer efficiency is increased.
Significant benefits accrue with automated control of dissolved oxygen (DO) concentrations and automated pressure control. Recognizing that DO concentrations are a function of air flow and variable biological oxygen demand (BOD), automated control processes can adjust the DO concentration to optimize energy consumption. Operating a system with excessive header pressure, e.g., by as little as 25 Torr, can increase power consumption by more than five percent. Automated pressure regulation can minimize such pressure excursions to further improve operating efficiencies.
In single stage blower designs which incorporate dual inlet and discharge vane control, control processes can be applied for independent management of the flow and head functions. The flow function can be managed through discharge control vanes and the head function can be managed via control of inlet guide vanes. This enables a relatively high operating efficiency over a relatively wide range of flow rates and temperature conditions.
Despite opportunities for realizing potentially large energy economies with the afore described technologies, there is a continued need to find additional means for improving operating efficiencies and to reduce capital expenses of treatment plants.
Like reference numbers are used to denote like features throughout the figures.